From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from buildserver.ru.mvista.com (unknown [213.79.90.228]) by ozlabs.org (Postfix) with ESMTP id 51E87B6F6F for ; Tue, 31 May 2011 03:25:45 +1000 (EST) Date: Mon, 30 May 2011 20:57:45 +0400 From: Anton Vorontsov To: Tabi Timur-B04825 Subject: Re: [rtc-linux] Re: [PATCH] Add support for pt7c4338 (rtc device) in rtc-ds1307 driver Message-ID: <20110530165745.GA2758@oksana.dev.rtsoft.ru> References: <1306393409-16153-1-git-send-email-Priyanka.Jain@freescale.com> <20110526091020.GA2201@pengutronix.de> <470DB7CE2CD0944E9436E7ADEFC02FE316DCB8@039-SN1MPN1-002.039d.mgd.msft.net> <20110530082429.GA3409@pengutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 In-Reply-To: Cc: "a.zummo@towertech.it" , "rtc-linux@googlegroups.com" , "p_gortmaker@yahoo.com" , Jain Priyanka-B32167 , "akpm@linux-foundation.org" , "linuxppc-dev@lists.ozlabs.org" List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Mon, May 30, 2011 at 02:29:58PM +0000, Tabi Timur-B04825 wrote: > On Mon, May 30, 2011 at 3:24 AM, Wolfram Sang wrote: > > > The first place where this should be mentioned is the datasheet of the > > pt-chip, so you might ask the producer to add this information (don't > > expect much to happen, though). > > It's true that the data sheet does not mention that it's identical to > the DS1307, but that's still no excuse for not noticing it and writing > a whole driver for it. :-( > > > IIRC I asked you explicitly for the differences between the chips. If > > there are none, you can use the driver directly, right? :) > > Yes. The device tree node for the PT7C4338 device should just say > > /* The board has a PT7C4338, which is compatible with the DS1307 */ > compatible = "dallas,ds1307"; While it seems to be 100% compatible, there could be chip-specific bugs or some interesting features that are hidden behind "reserved" bits and registers. So I think device tree should not lie about the chip model. Doing 'compatible = "pericom,pt7c4338", "dallas,ds1307"' is perfectly fine. Note that today the several compatible entries approach gives you almost nothing, as you will need to add pt7c4338 entry into the driver anyway. I tried to improve this, i.e. make linux do OF-matching on the most generic compatible entry (the last one): http://www.mail-archive.com/linuxppc-dev@lists.ozlabs.org/msg21196.html It was received coldly though: http://www.mail-archive.com/linuxppc-dev@lists.ozlabs.org/msg22041.html http://www.mail-archive.com/linuxppc-dev@lists.ozlabs.org/msg21273.html -- Anton Vorontsov Email: cbouatmailru@gmail.com